Core nest



Jan. 14, 1969 A. R. HANSON ETAL 3,421,865

CORE NEST Sheet Filed Jan- 5, 1966 INVENTORS ALA/V R. HANSON PAUL R. M/NKS OLIVER M. MOE

TT EY Jan. 14, 1969 A. R. HANSON ETAL 2 CORE NEST Filed Jan. 3, 1966 Sheet 2 of z TRIMMING CHEMICALLY MACHINABLE PANEL To A DIM ROUGH ENSIONS CLEANING B PANEL APPLYING PHOTO- RESIST PRINTING DESIRED APERTURE CONTOUR D DEFINING PATTERN DEVELOPING DESIRED APERT CONTOUR E DEFIN PATTERN BURNING-IN OF IRED APERTURE co UR F DEFINING PATTERN CLEANING G PANEL ETCHING 'DEsIR APERTURE CONT H PATTERN Y o 0 CLEANING I I PANEL 1 ALLA TRIMM PANEL "82 To AL I J I DIMENSIONS :2;

United States Patent 5 Claims ABSTRACT OF THE DISCLOSURE A planar tooling jig having a plurality of apertures therethrough, or cavities therein. The jig has particular application as a core nest for aligning toroidal memory cores during the mechanized core-stringing operation. The apertures, or cavities, which are chemically machined in a single sheet, have a bone-shaped planar cross-section for providing chordal nesting of the cores and for avoiding corner radii interference.

It is well known that in the field of electronic data processing the means utilized to store binary data is generally comprised of a plurality of two-dimensional arrays of toroidal ferrite cores. These toroidal cores are generally arranged in a plurality of orthogonally arranged rows and columns with a separate core at each rowcolumn intersection. Drive lines are threaded through the central apertures of the toroidal cores along the rows and columns and terminate at suitable terminals on a core array supporting frame. The threading of the drive lines through the central apertures of the toroidal cores, commonly referred to as core stringing, requires the use of a tooling fixture termed a core nest that provides a tooling function for maintaining the alignment of the toroidal cores during the core stringing operation.

With the advent of the use of increasingly larger memory core arrays in the electronic data processing field it has been necessary to mechanize the core stringing operation to reduce the cost of a memory core array when fabricated by previously utilized hand stringing techniques. In the copending patent of Frederick A. Fielder et al., Patent No. 3,331,126, issued July 18, 1967, there is disclosed a core stringing machine that simultaneously threads all the lines along the parallel sets of rows or columns of a two-dimensional array of toroidal cores. This core stringing machine may utilize as a core nest a device such as disclosed in the N. B. Mears Patent No. 3,174,837, which core nest is comprised of a laminar plate having a plurality of apertures therethrough arranged in a predetermined pattern of rows and columns wherein each of said apertures conforms to the diametrical cross section of the cores to be set therein. Further, each of said apertures has a smaller aperture therethrough whereby a vacuum is supplied from the underside of such core nest for securely holding the toroidal cores in the rectangularly shaped apertures.

As the toroidal cores utilized in modern day memory arrays are of extremely small sizeone core presently utilized is 0.023 inch O.D. times 0.015 inch I.D. times 0.0057 inch thick-it has been necessary to form the core nest apertures by a chemical etching process. As the crosssectional form of the to-be-chemically-machined aperture has been difiicult to maintain through any substantial depth due to problems of undercutting, overcutting, and minimum obtainable corner radii such chemical machining of the core nest apertures has been limited to single sheet planes of a thickness insufiicient to individually provide sufiicient structural rigidity and depth to perform the nesting function. Such core nests have been built up in a 3,421,865 Patented Jan. 14, 1969 laminar manner of a plurality of like-arranged apertures whereby the laminar structure so formed provides sulficient structural rigidity to perform the nesting function while the individual apertures in the separate'larninar sheets can be held to the desired aperture cross-sectional contour. The primary problem occasioned by the use of the chemical machining process is that as the machining depth increases the minimum corner radii increases such that the aperture, or cavity, soon approaches a race track configuration with increasing depth while the aperture planar contour will not conform to a square cornered rectangle of the desired cross-section. Although the use of a laminar structure including a bottom vacuum plate does obviate the bottom corner radii problem occasioned by chemical machining the problem occasioned by the necessary alignment of the plurality of apertures in the superposed laminar sheets does not permit the efficient and economical fabrication that might be achieved by the use of a core nest consisting of a single layer of chemically machinable material.

The present invention in its preferred embodiment relates to a core nest that provides a tooling function for the alignment of toroidal cores during the mechanized core-stringing operation. The preferred embodiment of the core nest of the present invention is comprised of a single sheet of chemically machinable material having a plurality of bone shaped apertures. These bone-shaped apertures are generally of a four sided form having a length greater than the width thereof whereby opposing surfaces are convexly arcuate providing four rectangularly oriented points for orienting the associated toroidal core. These apertures permit chordal nesting of the cores therein while permitting a desired rotation of the nested cores along a diameter normal to the plane of the core nest so as to facilitate the core stringing operation. By providing a bone-shaped cross-sectional aperture of a length less than the diameter of the core to be used the core is supported on the end edges of the aperture opening rather than allowed to bottom in the aperture as in prior art devices. By using the chordal nesting of the core the apertures bottom corner radii to not reduce the effective width or length of the aperture. Further, by using the bone-shaped cross-section wherein the aperture corner radii are effectively moved out from the aperture proper the minimum corner radii produced by the chemical machining operation do not interfere with the chordal cross-section of the nested core. This permits the nested core to be maintained in a fixed but yielding manner by the central, narrower portions of the apertures. These central narrower portions permit the nested core, when influenced by a winding being threaded therethrough, to rotate in a yielding manner providing a larger projected opening of the toroidal cores central aperture to the influencing winding. Additionally, by using a core nest of a single sheet the orienting problems inherent in the assembling of a laminar core nest are obviated.

According, it is a primary object of this invention to provide a novel core nest.

It is a further object of this invention to provide a core nest that is comprised of a single sheet of chemically machinable material having a plurality of bone-shaped apertures therethrough that permit chordal nesting of the cores therein while permitting a desired rotation of the nested cores along a diameter normal to the plane of the core nest so as to facilitate the core stringing operation.

These and other more detailed objectives will be disclosed in the following specification, reference being had to the accompanying drawings.

With particular reference to FIG. 1 there is illustrated a preferred embodiment of a planar core nest incorporating the present invention. Core nest 10 is comprised of a single sheet 12 of a chemically machinable material such as a photoengravers type copper sheet having one planar surface back-coated with a chemically resistance layer to preclude chemical reaction thereto during the chemical machining process. Core nest has a plurality of bone-shaped apertures 14 therethrough arranged in a predetermined pattern along orthogonally-arranged parallcl-sets of column and row axes forming a grid pattern of apertures 14. These column and row core stringing axes are drawn at a 45 angle to the aperture 14 lOng axis such that such serially aligned apertures 14 are arranged at an angle of 90 to each other. Accordingly, toroidal cores oriented thereby present a 45 angle projection along the core stringing axes to memory core drive lines during the mechanized core stringing operation as more fully discussed in the aforementioned Fielder, et al., patent. Additionally, a plurality of holes 16 provide the means whereby core nest 10 may be supported in its various uses. In the illustrated embodiment sheet 12 is of a thickness of 0.030 inch; however, no limitation thereto is intended. As will be more fully apparent such thickness is dictated by many factors including the required structural rigidity and the size of the apertures 14 therethrough.

With particular reference to FIG. 2 there is illustrated a detail of the planar contour of apertures 14 and their spatial relationship along the various axes employed. Apertures 14 have a bone-shaped planar contour which contour avoids many problems previously encountered in prior art chemical machining processes. As the physical dimensions of the apertures, or cavities, to be formed in a planar substrate member are reduced in size the only practical method of forming such apertures, or cavities, to the required dimensional quality is by a chemical machining process such as photoetching. However, the minimum planar corner radii that can be obtained by a chemical machining process may approach the apertures minimum dimensions whereby in a to-be-desired rectangular aperture planar contour the apertures internal corner radii produces a race track contour due to the inability to chemically machine square corners. In tooling devices requiring extremely small apertures, or cavities, for the orientation of the elements therein wherein such elements have a substantially rectangular cross-section, such as toroidal ferrite cores, such relatively large internal corner radii require that the apertures principal dimensions be increased to accommodate the square cornered element. This necessity for larger-than-necessary apertures provides many obvious problems including the loss of orienting integrity.

The primary use of the tooling device of the present invention is a core nest for the orientation of a plurality of toroidal cores in a core stringing operation. It has, in the past, been required to make such core orienting apertures sufiiciently larger in cross section than the toroidal core it is to orient, so that the aperture is able to accommodate a substantially square cornered toroidal core. Additionally, as the internal corner radius increases with increased cavity depth the bottom corner radius becomes objectionably large. Accordingly, it has been the prior art practice to fabricate a core nest in a minimum of two separate parts; the main body portion having the core orienting aperture therethrough; and a bottom vacuum plate having a still smaller aperture therethrough to permit access of the vacuum source into the larger core orienting aperture. In these prior art arrangements the oriented toroidal core bottoms upon the bottom vacuum plate thus establishing the vertical orientation in the core orienting aperture while relying upon the sides to the core orienting aperture to estabilsh horizontal orientation-see the above discussed Mears Patent No. 3,174,837.

Applicants bone-shaped aperture 14 overcomes these prior art difficulties in two ways:

(1) By increasing the aperture width in the end areas the minimum corner radii have no effect upon the orientation of the to-be-oriented core, such end area planar contour effectively decreases the internal corner radius to zero;

(2) By decreasing the apertures length along a central axis to a chordal dimension of the core, i.e., to less than the cores outside diameter (O.D.), the core is caused to rest upon such apertures top planar end edges thus effectively eliminating the bottom corner radii problem previously requiring the use of a separate bottom vacuum plate. As the top planar contour of the core orienting aperture, or cavity, is accurately definedas compared to the internal contour-by the chemical machining process, such as photoetching, a highly accurate and precisionlike tooling jig is made possible by the novel planar contour of applicants bone-shaped aperture.

With particular reference to FIG. 3 there is illustrated a cross-section of aperture 14 taken along the major axis thereof. FIG. 3 illustrates that core 20 rests on the top planar contour end edges 22 of aperture 14 which end edges 22 are spaced a chordal distance 24 of core 20 such that the central aperture 26 of core 20 is preferably slightly below the top surface of sheet 12. This chordal distance 24 is an empirically determined quantity that is a function of the particular core used with core nest 10 but which in most applications is of a sufficient quantity to provide an optimum opening of the cores central aperture to the drive line that is to be threaded therethrough at a 45 angle. As can be seen here, the internal contour of aperture 14 has no effect upon the orientation of core 20 in aperture 14.

With particular reference to FIG. 4 there is illustrated a cross-sectional view of aperture 14 taken along a minor axis thereof. FIG. 4 illustrates that core 20 is oriented in the horizontal plane with respect to aperture 14 by substantially only the top planar contour side edges 28 of aperture 14. As can be seen here the internal contour of aperture 14 has substantially no effect upon the orientation of core 10 in aperture 14.

With reference back to FIG. 2 it can be seen that core 20 is oriented in aperture 14 by substantially arcuate opposing end edges 22 and substantially arcuate opposing side surfaces 28. These arcuate edges and surfaces permit a slight rotation of core 20 about a vertical axis centrally oriented through aperture 14. This permissible slight rotation of core 20 may be utilized to advantage during a core stringing operation. As an example, as the to-bethreaded drive line approaches a core at a 45 angle it may strike the edge of core 20 causing a jigging action of core 20 about its vertical axis whereby the drive line is aided in its passage into the cores central aperture 26. Additionally, upon attempting to pass through the cores central aperture 26 a drive line may strike the opposite inside surface of aperture 26 causing a jigging action of core 20 about its vertical axis whereby core 20 rotates away from the drive line aiding its passage therethrough.

Element 10 is formed in the preferred embodiment in the following steps as diagrammed in Steps A-J, FIG. 5:

Step A.The base element of core nest 10 is planar sheet 12 of photoengravers type copper panel of 0.03 inch in thickness back-coated with a chemically resistance layer to preclude chemical reaction thereto during the chemical machining process while the top or front surface is a polished surface treated to prevent oxidation.

Step B.The copper sheet 12 of the desired dimensions is then cleaned by any suitable commercial solvent prior to the addition, on the top surface, of the photo-resist. In the procedure followed by the applicants, sheet 12 is fixed in a Whirler-Coater, manufactured by the Master Etching Machine Company, Wyncote, Pennsylvania, while a solution of circuit board cleaner, such as Fremont No. 328 manufactured by Fremont Industries, Inc., Mineapolis, Minn., is placed upon the top surface of sheet 12 and with the aid of running tap water and a soft vegetable bristle brush the top surface is scrubbed until it shows no water breaks. Sheet 12 is then thoroughly flushed with tap water followed by a quick flush with distilled water just prior to the application of the photo-resist.

Step C.-Next, is the application of the photo-resist. With sheet 12 still mounted on the Whirler-Coater mounting panel and with sheet 12 revolving at a velocity of 80 rpm. a commercial photo-resist solution is poured on the center of sheet 12. The centrifugal force established by the revolving mounting panel causes the photo-resist to flow evenly out over the top surface of sheet 12. The photo-resist solution used by applications is a Koper-Top enamel mixture having a base to sensitizer ratio of approximately 1 to 9 and is manufactured by Chemco-Photo Product Company, Inc., Glen Cove, N.Y. Lastly, the photo-resist is dried by the Whirler-Coater heat lamps for a period of approximately 15 minutes.

Step D.Next, is the printing operation. A photo-negative having a predetermined arrangement of the desired aperture contour defining pattern and which is prepared by any well-known means is placed upon the top surface of sheet 12 between it and the to-be-used light source. The Colight printer used by applicants is manufactured by Colight, Inc., Minneapolis, Minn., and requires'a six minute printing time for applicants procedure; however, such printing time is a function of many variables and must be determined empirically for each operation.

The apertures contour defining pattern is illustrated in FIG. 5, Step D and is in the form of a double-ended Y and is utilized to provide the novel bone-shaped planar contour of the present invention. The pairs of the angled legs extending from both ends of the base line permit the etching solution to form the relatively wider end portion characteristic of applicants bone-shaped aperture; although applicants in the preferred method use straight line segments to form the double-ended Y pattern no limitation thereto is intended, as an example curved, semicircular end segments could be utilized.

Step E.-Next is the development step for forming the predetermined arrangement of the aperture contour-defining pattern upon the top surface of sheet 12. Sheet 12 is reinstalled in the Whirler-Coater and the top surface of sheet 12 is flushed with tap water. As water is the developing agent of the Koper-Top photo-resist, the aperture contour-defining-pattern established by the printing operation of Step D above is developed by the tap water fixing the surfaces of sheet 12 set by the light of the printing operation while flushing away the Koper-Top photo-resist not set by the light of the printing operation, it conforming to the photo-negative pattern of Step D. What remains is a layer of fixed Koper-Top photo-resist having a pattern of aperture contour-defining-apertures therethrough to the base copper of the top surface of sheet 12, which pattern may additionally include apertures defining any desired holes or cavities of sheet 12 such as mounting holes 16 of FIG. 1.

Step F.Next is the burning-in of the photo-resist. The panel of Step E is placed into a suitable oven having a stabilized temperature of approximately 550 to 650 F. The panel is submitted to this temperature until the photoresist becomes a medium chocolate brown color which is the indication of proper burn-in. The time required may vary between wide limits of approximately 10 to 30 minutes.

Step G.Next is a cleaning step in preparation for the etching step. For the cleaning of sheet 12 it is first rinsed in a De-Scum solution manufactured by Chemco-Photo Product Company, Inc., Glen Cove, N.Y., rinsed with tap water and then installed in the etching machine.

Step H.Next is the etching step wherein apertures conforming to the predetermined arrangement of the desired aperture contours of FIG. 2 are achieved. The panel of Step F above is installed in a suitable etching tank having the desired etching solution therein whereby the etchant is splashed against the exposed copper surfaces of sheet 12 chemically machining away such exposed copper surfaces. In applicants method, sheet 12 is installed on the underside of the cover of a Master Etcher, manufactured by the Master Etching Company, Wyncote, Pennsylvania, with the etchant solution splashed upon the exposed copper surfaces of sheet 12 by the internal, rotating paddle wheels.

The etching step is the most critical step in the present method. As is well known an etchant has a tendency to undercut or overcut, i.e., remove less or more of the base material, the base material-copper in the preferred embodiment-as the etchant chemically machines away the exposed copper while increasing the depth of the so-formed cavity. Consequently, the use of a plain etchant solution such as ferric chloride provides poor aperture contour resolution with increase in aperture depth. In this step of applicants method, applicants use a basic etchant solution of ferric chloride and add thereto, as a controllant, a quantity of Peri-additive, manufactured by the Phillip A. Hunt Chemical Corporation, Palisades Park, N.J., and secondary additives which are designed to improve the etchant solution; see Handbook of Photoengravers Research Institute, Inc., 2447 Western Ave. Park Forest, Ill. Peri-additive is added to the basic etchant solution to control the degree of under or overcutting achieved by the basic etchant solution. By empirical, trial and error methods the proper proportion of basic etchant solution and Peri-additive is determined for the particular machining requirements whereby a substantially straight sided aperture, such as shown in FIGURE 3 and 4, may be achieved. However, the addition of the Peri-adidtive to the basic etchant solution does not decrease the minimum internal corner radii that, as stated hereinbefore, presents dimensional problems in prior art devices.

Step I.--Next is a cleaning step in preparation for trimming to final dimensions. For the removal of the etchant solution of Step H FIG. 5, sheet 12 may be washed with a hot solution of sodium hydroxide and scrubbed with a soft brass-bristle brush.

Step J.Lastly is the final machining operation for trimming sheet 12 to final dimensions.

As an alternative method to applicants preferred method described above, the following changes to such preferred method may be made. If it is desired that the panel of sheet 12 be of an initial thickness greater than the final desired thickness the following alternative pro cedure may be followed:

Step 1.During Step H, FIG. 5, the etching or chemical machining process may be terminated when the etchant solution has generated cavities of the desired depth.

Step 2.After a cleaning operation similar to Step I, FIG. 5, the bottom surface of sheet 12 is machined away by any well-known machining method to establish the desired final thickness of sheet 12. At this thickness the cavities may or may not break through the machined surface leaving a ragged edge about the cavity walls due to the bottom corner radii or leaving a thin section between the cavity bottom and the machined surface.

Step 3.Next, the cavities are coated with paraffin to preclude the effect therein the etchant solution of the next steps.

Step 4.-Next, a cofferdam is constructed around the edges of the machined surface.

Step 5.Next, a nitric acid solution is added to the coffer-dam. It is allowed to set for a period of time to sufficiently chemically mill out the material of sheet 12 between the cavity walls and the machined surface left by Step 2 above.

Step 6.Lastly, the paratfin of Step 3 above is removed and the finished panel is cleaned as in Step I, FIG. 5.

It is understood that suitable modifications may be made in the structure as disclosed provided such modifications come within the spirit and scope of the appended claims. Having now, therefore, fully illustrated and described our invention, what we claim to be new and desire to protect by Letters Patent is set forth in the appended claims.

7 What is claimed is: 1. A planar core nest having a plurality of apertures for orienting a plurality of toroidal cores therein, the core nest comprising:

a single sheet of chemically machinable material having a plurality of bone-shaped apertures therein;

said apertures generally of a four sided form having a length greater than the width thereof with the opposing top planar surfaces being convexly :arcuate for providing four rectangularly oriented points for orienting the associated cores on a chordal dimension along said length in a fixed but yielding manner above the bottom of said apertures.

2. A planar core nest having a plurality of openings on a top planar surface, for orienting a plurality of toroidal cores therein, the core nest comprising:

a single sheet of chemically machinable material having a plurality of bone-shaped openings on the top planar surface thereof;

said openings generally of a four sided form having a length greater than the width thereof with the opposing top planar surface edges for orienting the associated cores on a chordal dimension along said length in a fixed but yielding manner above the bottom surface of said sheet.

3. A planar core nest having a plurality of openings on a top planar surface for orienting .a plurality of toroidal cores therein, the core nest comprising:

a single sheet of chemically machinable material;

said sheet having a plurality of boneshaped cavities therein;

each of said cavities generally of a four sided form having a length greater than the Width thereof With the opposing top planar surface edges being convexly arcuate for providing four rectangularly oriented points for orienting an associated core on a chordal dimension along said length in a fixed but yielding manner above the bottom planar surface of said sheet.

4. A planar core nest having a plurality of openings on a top planar surface for orienting a plurality of toroidal cores therein, the core nest comprising:

a single sheet of chemically machinable material;

lit

said sheet having a plurality of bone-shaped cavities therein;

a plurality of toroidal cores, an associated one oriented in each of said cavities;

each of said cavities generally of a four sided form having a length greater than the width thereof with the opposing top planar surface edges being convexly arcuate for providing four rectangularly oriented points for orienting said associated core on a chordal dimension along said length in a fixed but yielding manner above the bottom planar surface of said sheet.

5. A planar core nest having a plurality of apertures therethrough for orienting a plurality of toroidal cores therein, the core nest comprising:

a single sheet of chemically machinable material having a plurality of apertures therethrough;

a plurality of toroidal cores, an associated one oriented in each of said apertures;

each of said apertures having a bone-shaped opening in the top planar surface of said sheet, said opening having a generally rectangular form having a length greater than the width thereof with the opposing top planar surface edges being convexly arcuate for providing four rectagularly oriented points for orienting the associated core on a chordal dimension along said length in a fixed but yielding manner above the bottom planar surface of said sheet.

RCA Technical Notes, Vesper A. Schlenker, Mounting for Magnetic Memory Cores, RCA TN #190.

HYLAND BIZOT, Primary Examiner.

J OE LEGRU, Assistant Examiner.

US. Cl. X.R. 

